1. Field of the Invention
The present invention relates to a charge/discharge control circuit for controlling charge/discharge of a secondary battery, and a battery device, and more specifically, to a charge/discharge control circuit having a self-test function for a voltage detection circuit for detecting a voltage of a secondary battery, and a battery device.
2. Description of the Related Art
A battery device is used as a voltage supply source for circuits of various electronic devices. In recent years, the battery device has been required to output a high voltage as a power supply for automobiles and electric tools. Therefore, there is needed a battery device in which a plurality of secondary batteries are connected in series and which includes a plurality of cascade-connected charge/discharge control circuits for controlling charge/discharge of the secondary batteries (see, for example, Japanese Patent Application Laid-open No. 2009-17732).
FIG. 4 illustrates a block diagram of a conventional battery device including series-connected secondary batteries and cascade-connected charge/discharge control circuits for controlling the secondary batteries.
The conventional battery device includes a plurality of cascade-connected charge/discharge control circuits 401a to 401n, a plurality of series-connected secondary batteries 402a to 402n, a charge control FET 403, a discharge control FET 404, resistors 405a to 405n each connecting a charge control terminal CO and a charge control signal input terminal CTLC, and resistors 406a to 406n each connecting a discharge control terminal DO and a discharge control signal input terminal CTLD.
In the conventional battery device, the charge/discharge control circuits 401a to 401n are connected to each other via the charge control terminal CO and the charge control signal input terminal CTLC and via the discharge control terminal DO and the discharge control signal input terminal CTLD, thus enabling reciprocal communication. In this manner, the plurality of charge/discharge control circuits can be connected in series, and hence a necessary number of series-connected secondary batteries for outputting a high voltage can be controlled.
In the above-mentioned battery device, however, the number of voltage detection circuits increases as the number of secondary batteries increases. Therefore, there has been a drawback that a device for testing each voltage detection circuit becomes complicated in the state of being assembled as a battery device.